Polymeric foams include a plurality of cells (or voids) formed within a polymer matrix. Microcellular foams (or microcellular materials) are polymeric foams which have very small cell sizes and high cell densities. By replacing solid plastic with voids, polymeric foams use less raw material than solid plastics for a given volume. Thus, raw material savings increase as the density of a foam decreases.
Blown film extrusion is a common technique to make polymer films. The process generally involves extruding a tube of molten polymer through a die and inflating the tube to several times its initial diameter to form a thin film bubble. This bubble is then collapsed and formed into a film.
Blown film generally has a better balance of mechanical properties than cast or extruded films because the film is drawn in both the transverse and machine directions. However, when blowing polymer foam films, it can be challenging to maintain a good cell structure because there is a tendency to distort the foam cells during the blowing process.
Accordingly, a technique for producing a polymeric foam film having a quality cell structure would be desirable.